The blue field entoptic phenomenon is a visual perception of "flying" corpuscles in an observer's eye when that observer looks into a bright, deep-blue light. Ophthalmic diagnostic devices incorporating this phenomenon are well known in the art. Such devices have been used to diagnose various eye diseases such as amblyopia, diabetes, glaucoma, etc.
Furthermore, it has been reported that by observing the blue field through a rotating artificial pupil, an observer may perceive his or her own retinal vessels, including the foveal avascular zone (FAZ). This can be very useful, since the ability to accurately measure the size of the FAZ can provide a means for following the progression of some ocular diseases, e.g. diabetic retinopathy.
It has also been reported that causing the aforementioned bright, deep-blue light to flicker can induce changes in the blood flow characteristics of the retina.
One example of a prior art blue field diagnostic device is the Blue Field Simulator marketed by Oculix Inc. This device allows an observer to determine the number of corpuscles, their speed, and their pulsatility (i.e., their responsiveness to systolic and diastolic heart function) as the corpuscles pass through that observer's own retina.
The measurement technique utilized by the Oculix device consists of two steps.
First, the observer is asked to switch back and forth between two computer simulated screens displayed on the same computer monitor. The first screen is a reference screen displaying pre-determined corpuscle-like particles whose associated parameters are known only to the operator. The second screen is an adjustable screen, displaying adjustable corpuscle-like particles that the observer must adjust so as to match, from his or her own memory, the pre-determined corpuscle-like particles displayed on the first screen. By comparing these adjustment values, the operator can evaluate the reliability of the observer's responses.
Second, the observer is then asked to do the same operation, but this time comparing between a deep blue field (which causes the observer to perceive his or her own real corpuscles) and the aforementioned adjustable screen (which presents operator-adjustable corpuscle-like particles). The results are then evaluated, beating in mind the reliability results obtained from the first step.
Unfortunately, the foregoing procedure is quite tedious and time consuming to perform. In addition, it is not suitable for every observer. For example, in some instances the reliability of the results obtained in the second step can not be deduced directly from the test results obtained in the first step. This is typically because the real corpuscles may differ significantly from the simulated corpuscles, and also because of the reliance placed upon the short term memory of the observer. In addition, because the simulated corpuscle-like particles displayed on the computer monitor of the Oculix machine have a lower contrast and brightness than the entoptically viewed real corpuscles, it can be difficult for observers having lower visual acuity (e.g., from diabetes or cataracts) to see the simulated particles.
In addition to the foregoing, the Oculix prior art device does not allow for either the determination of the size of the foveal avascular zone (FAZ) or the measuring of changes in the observer's blood flow characteristics due to blue light flicker stimulation.